Field of the Invention
The present invention concerns a system comprising a multifocal diffractive lens component. In particular the invention relates to a system comprising a diffractive lens component configured to be simultaneously bifocal. The invention further relates to a method of determining a simultaneously bifocal diffractive system comprising a lens component.
Applications of the present invention can be found in the fields of vision improvement and correction of vision defects. Ophthalmic lenses are worn and widely used for the correction of various types of vision deficiencies. These include defects such as near-sightedness (myopia), farsightedness (hypermetropia), astigmatism, and defects in near-range vision usually associated with aging (presbyopia).
In the context of the present invention the term ophthalmic lens refers to vision correction lens such as a spectacle lens, a contact lens, an intraocular lens, an artificial cornea and the like.
Description of the Related Art
Ophthalmic lens include multifocal lenses in which a first region of the lens is designed to have a first focal length and another different region of the lens is designed to have a second focal length different to the first focal length. Typically one of the focal lengths corresponds to a focal length for viewing far objects and another focal length corresponds to a focal length for viewing near objects. Accordingly, a near vision (NV) zone corresponds to the surface area of the ophthalmic lens including the points of intersection of the lines of sight of the user for near distance vision such as reading and the far vision zone (FV) corresponds to the surface area of the ophthalmic lens including the points of intersection of the lines of sight of the user for far distance vision for viewing distant objects. Such multifocal ophthalmic lens include bifocal lenses having a far vision zone and a near vision zone and progressive lenses which have a far vision zone, a near vision zone, and an intermediate zone between the far vision zone and the near vision zone, with a principal progression meridian crossing the three zones. Multifocal lenses are often used for the correction of vision defects caused by presbyopia.
Other types of bifocal lens are configured for simultaneous bifocal vision.
In some cases such lenses have an inner zone having a first focal length and an outer annular zone surrounding the inner zone having a second different focal length. Light passing through the inner zone forms an image at the first focal length and light passing through the outer zone forms an image at the second focal length. One of the images is projected onto the retina of the eye of the user while the other image is simultaneously projected behind or in front of the retina. The human brain processes the visual signals received in such a way that the improperly focused image is ignored thereby giving the user the impression of one focused image.
The design of such lens provides many challenges in terms of quality of vision.